In U.S. Pat. No. 3,858,903 (issued Jan. 7, 1975), there is disclosed and claimed a leveling valve for an air spring suspension system comprising a damping chamber, an air control chamber and an actuator controlled spring return housing. A rotatable actuator shaft extends into the damping chamber, the air control chamber and a lateral bore in the spring return housing. The spring return housing is rotatably mounted on the actuator shaft and has an axial bore perpendicular to the lateral bore. A spring cup is reciprocably guided in the axial bore and is biased in contact with the actuator shaft. A flat surface is ground onto the actuator shaft in registry with the axial bore. The bottom of the spring cup seats on the flat surface of the actuator shaft so that rotation of the spring return housing with respect to the actuator shaft results in resilient movement of the spring cup within the axial bore of the spring return housing. Thus, on rotational movement of the spring return housing, a torque is applied to the actuator shaft tending to rotate the actuator shaft about its axis and thereby operate air valves to permit air to flow into or out of an air spring. The force of the edge of the actuator flat surface against the bottom of the spring cup tends to produce lateral as well as axial forces on the spring cup. If the tolerances between the axial bore and the spring cup are not extremely close, the spring cup will tend to move laterally and thereby forfeit a portion of what otherwise would be axial movement of the spring cup. This condition results in less or no torque on the actuator shaft. In order to provide for close tolerances between the axial bore and the spring cup, a machining operation is necessary on one or both of the axial bore or the outer surface of the spring cup. This machining operation is expensive and adds considerable labor cost to this part.
It is desirable to mold the spring return housing out of a plastic or to cast it from metal. In order to form the axial bore, a pin must be used in the mold. A draft angle must be provided along the length of the axial bore in order to remove the pin from the bore. The draft angle will necessarily result in more than desirable tolerance between the spring cup and the axial bore. Thus, a machining operation would be necessary in order to provide a perfectly cylindrical axial bore.